It has long been known that certain combat conditions subject the combatants to varying situations, requiring the rapid use of more than one sight or zero to accommodate for the conditions, such as when adapting for shooting in a horizontal plane to shooting at a steep angle, the utilization of day and night sights, or alternatively, when shooting from a crowded, cramped, protected position.
Historically, these varying conditions of combat engagement have been met by utilizing different weaponry, a situation which is unrealistic in most conditions, or in the alternative, utilizing quick exchange sighting mechanisms, which require the user to take the gun off target to exchange the sight, a time-consuming and perhaps life-endangering diversion.